Objective

1. Understand operation of relay and contactor2. Disassemble and identify function part of relays and contactor3. Draw various type symbol of relay(SPDT,DPDT,4PDT)

Introduction

A relay is an electrically switch Relay use an electromagnet to operate a switching mechanism

mechanically, but other operation principle are also used Relay are used where it is necessary to control a circuit by a low-

power signal(with complete electrical isolation between control and controlled circuit),or where a several circuit must be controlled by one signal.

The first relays were used in long distance telegraph circuit ,repeating the signal coming in from one circuit and re transmitting it to another.

Relays were used extensively in telephone exchanges and early computer to perform logical operation.

Contactor

A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current rating,

A contactor is controlled by a circuit which has mush lower power level than the switched circuit.

Contactor come in many form with varying capacities and features. unlike an circuit breaker, a contactor is not intended to interrupt a short circuit current.

Contactors range from those having a breaking current if several amps and 24V DC to thousand of amps and many kilovolts.

The physical size of contactors range from a device small enough to pick up with one hand to large devices approximately a meter on a side,

Contactor are use to control electrical motor, valve electromechanical timer and counter, actuator and other electrical loads.

Lab exercise

1. AC magnetic contactor

2. Relay3. Screw driver(plus or minus)

Lab Task 1

1. Remove the base of the contactor2. Take out the clip holder3. Remove hood cover of the contactor4. Remove the body cover5. Take the picture of the part inside the contactor6. Finally, labeled and briefly explain the part in the picture

Lab task 2

1. Remove the cover of the relay2. Take the picture of the part inside the relay3. Finally,labeled briefly explain the part in the picture

Lab task 3

1. Draw various type symbol of relay (SPDT,DPDT,4PDT)

2.

Conclusion

In this lab,we was learn A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles

are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations.